<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>下拉菜单</title>
    <link rel="stylesheet" href="./css/index.css" />
  </head>
  <body>
    <div class="menu">
      <h2>下拉菜单</h2>
      <ul class="sub-menu">
        <li>子菜单1</li>
        <li>子菜单2</li>
        <li>子菜单3</li>
        <li>子菜单4</li>
      </ul>
    </div>
  </body>
</html>
